The CheckValueChange method calls ImplCheckValueChange to determine whether the value of this adapter field has changed from the value originally retrieved from the database table. 

AActionRequest is the interface of the action request object. CheckOrigValue can use this interface to obtain information about the current request (such as the value of the hidden field that contains the original value). 

AFieldIndex is the index of this field in the set of field values that AActionRequest maintains. 

ImplCheckValueChange calls CheckOrUpdateValue to verify that the request contains a value that can be assigned to the associated database field. If so, it returns true. Although this does not truly reflect whether the value has changed, it is a conservative approach that ensures no valid changes to the image are lost. If the request contains no value, this method returns false, indicating no update. If the request contains an invalid value, this method raises an EAdapterFieldException exception. 

CheckValueChange 

Value 

CheckOrUpdateValue 

EAdapterFieldException